Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$82.60	9.345%	$90.319	$90.32	$90.30	$90.30
Purchase #2	$122.89	9.665%	$134.7673	$134.77	$134.75	$134.80
Purchase #3	$225.75	3.628%	$233.9402	$233.94	$233.95	$233.90
Purchase #4	$199.35	3.297%	$205.9226	$205.92	$205.90	$205.90
Purchase #5	$235.58	4.426%	$246.0068	$246.01	$246.00	$246.00
Purchase #6	$59.72	11.149%	$66.3782	$66.38	$66.40	$66.40
Purchase #7	$75.40	11.445%	$84.0295	$84.03	$84.05	$84.00
7 purchase totals =	$1,001.29		$1,061.3636	$1,061.37	$1,061.35	$1,061.30